1. Field of the Invention
This invention relates to a voltage generator, and particularly to a voltage generator for generating a predetermined voltage through the use of electromagnetic induction, based on a received signal.
2. Description of the Related Art
A voltage generator has been applied to various devices. Of cards (hereinafter called xe2x80x9cIC cardsxe2x80x9d) each having a semiconductor integrated circuit incorporated therein, which have been widely used as portable storage media in particular, it is known that the voltage generator is used in a card (hereinafter called xe2x80x9cnon-contact IC cardxe2x80x9d) capable of performing the transfer of data without having to use a contact terminal for an external signal.
The voltage generator built and used in the non-contact IC card generates a voltage through the use of electromagnetic induction, based on a signal transmitted from the outside of the non-contact IC card, for example. The voltage generated by the voltage generator is used as an operating voltage for other circuits (such as a semiconductor integrated circuit) incorporated into the non-contact IC card. This operating voltage is used as a source voltage or data to be processed by the semiconductor integrated circuit. This type of voltage generator has been disclosed in the following references:
(1) Japanese Patent Application Laid-Open No. Hei 4-23092
(2) Japanese Patent Application Laid-Open No. Hei 10-97601
As is understood from each disclosure referred to above, the voltage generator using electromagnetic induction is constructed so as to obtain a predetermined voltage, based on alternating current signals produced by a coil corresponding to a receiving circuit. Therefore, there may be a case in which when the distance between a coil of an external device (e.g., card reader/writer) and the coil of the voltage generator increases, a voltage or current based on ac signals produced by the coil of the voltage generator is not achieved to a level enough to produce an operating voltage. There has recently been an increasing demand for a voltage generator for generating a voltage having a sufficient level as an operating voltage, regardless of the distance between the external device and the voltage generator.
In order to meet the demand referred to above, an increase in the cost and an increase in the area for the voltage generator may desirably be avoided to the utmost.
Further, the voltage generator may desirably generate a voltage having a stable level as an operating voltage.
An object of the present invention is to provide a voltage generator for generating a voltage having a sufficient level as a required predetermined voltage.
Another object of the present invention is to implement the voltage generator for achieving the above object, by reducing an increase in the cost and an increase in the area for the voltage generator to the utmost.
A further object of the present invention is to implement the generation of a voltage having a stable level as a required predetermined voltage by the voltage generator for achieving the above object.
According to one aspect of this invention, for achieving the above objects, there is provided a voltage generator for generating a predetermined voltage by electromagnetic induction, based on a received signal, which comprises a receiving circuit for receiving alternating current signals through the use of the electromagnetic induction, a rectifier circuit electrically connected to the receiving circuit and for rectifying the alternating current signals, a boosting circuit for boosting the signals rectified by the rectifier circuit, and a smoothing circuit for smoothing a signal boosted by the boosting circuit to thereby generate a predetermined voltage.
Typical ones of various inventions of the present application have been shown in brief. However, the various inventions of the present application and specific configurations of these inventions will be understood from the following description.